1. Field of the Invention
This invention relates to air conditioners and in particular to means for controlling the operation of air conditioners, such as central air conditioners, having outdoor condenser and compressor units and indoor evaporator and thermostatic control units.
2. Description of the Prior Art
Central air conditioners conventionally employ outdoor condenser and refrigerant compressor units which are connected to indoor evaporator units and controls by suitable ducts and wiring for providing relatively high capacity indoor air conditioning. Such systems utilize thermostatic controls which conventionally incorporate manually adjustable means for selecting a desired indoor temperature and automatically controlling the operation of the system to obtain such temperature.
At times, such air conditioning systems may become inoperative for any one of a number of different reasons. Illustratively, the system may be shut down because of a high thermostat setting. Alternatively, the apparatus "Heat-Off-Cool" on-off switch may not be in the "Cool" position. Further, power to the system may be disrupted or the voltage of the power supply may drop to a low level insufficient to permit operation of the system. The power interruption may be momentary or continuous.
Additional malfunctioning problems may arise from clogged air filters, furnace blower or evaporator coils. Malfunctioning of the furnace blower, such as from a blown fuse or a broken drive belt, may also cause a failure of the system. Additionally, where adjustable registers are utilized in the air distribution system, restricted, obstructed, or closed registers may similarly cause a failure of the system.
Additional failures may occur because of failure of the power supply to the outdoor condensing unit. Alternatively, such systems are caused to be inoperative when the outdoor temperature in below a preselected temperature, such as 60.degree. F. A restriction or obstruction of the outdoor condensing unit coil may further cause malfunctioning of the system.
Such malfunctionings heretofore have ordinarily required a check of the system by a service technician inasmuch as the prior systems did not provide for indicating to the user specific information as to the cause of the failure, permitting the user, in certain instances, at least, to remedy the malfunction. The requirement of a service technician, in many cases, has been unnecessary, time-consuming, and costly. It is obviously desirable to permit the user of the apparatus to effect simple restarting of the apparatus where the malfunction is of a simple nature so as to avoid the need for the services of a service technician. It is further desirable to provide to the user some indication as to the nature of the malfunction so that suitable servicing of the apparatus, of which the normal user is capable, can be effected without the need for the services of a service technician. Alternatively, where the malfunction is of the type that should be handled by a service technician, it is desirable to provide an indication of this fact to the user so as to avoid undesirable attempts by the user to restart the system without such service technician services. Further, the indication of the malfunction facilitates repair of the air conditioner by the service technician.
Because of the present energy crisis, the problem of low voltage conditions is becoming more prevalent. Such power supply conditions may cause permanent damage to the system. However, it has been found that, quite often, the low voltage condition is temporary and, thus, it is desirable to provide some means for preventing the air conditioner from starting under low voltage conditions and automatically resetting the system upon restoration of the preselected minimum voltage. Additionally, where the stoppage of the system is caused by a power interruption, it is desirable that the system be automatically restarted upon restoration of the power.
In the case of the other above discussed malfunctionings, the user must make some correction to the system prior to the restarting of the system and, thus, a manual reset of the system is desirable. Thus, before restarting the system where the malfunctioning has occurred because of clogged filters, evaporator coils, outdoor condensing unit coils, blown fuses, etc., these conditions must be corrected before an attempt to restart the system should be made.
A number of prior art patents disclose different controls for use with air conditioning apparatus. Thus, in U.S. Pat. No. 2,826,044 of Guy J. Reer, an alarm mechanism for refrigeration systems is disclosed having a multi-purpose alarm mechanism energized when the supply of refrigerant is low as well as for a number of other reasons. The control more specifically monitors the pressures in the suction and liquid lines.
John H. Heidorn in U.S. Pat. No. 3,047,696 shows a superheat control which is operable when subjected to superheat in the suction line or the compressor such as due to a leak of refrigerant from the system.
In U.S. Pat. No. 3,204,423 of Roy E. Resh, Jr. an air conditioning and refrigeration system control is shown incorporating a thermistor probe shifting the balance point of a primary temperature controller as a function of a heavy load condition of the apparatus.
Joseph N. Long in U.S. Pat. No. 3,232,519 shows a compressor protection system wherein temperature sensing means are located in the suction and discharge lines of the compressor with associated controls indicating an outrange temperature condition for selectively shutting down the compressor. The control further alternatively indicates the failure of a sensor.
Ernest A. Erickson in U.S. Pat. No. 3,427,818 shows an electronic control having an icing sensor preventing energization of the system when a freeze-out condition occurs therein. The cooling device and blower fan are controlled by both a temperature sensor and a photoelectric cell.
In U.S. Pat. No. 3,628,346 Cecil G. Lagrone, Jr. discloses an apparatus for indicating thermal and air velocity conditions of air in the plenum of a central air conditioning system such as upon a malfunction or failure of the fan or motor compressor of the system.
In U.S. Pat. No. 3,641,546 Richard D. Blackburn discloses the use of comparators for energizing an alarm device.
John Tsoras et al in U.S. Pat. No. 3,688,295 show an electronic temperature monitoring system having a comparator utilizing a hysteresis effect to prevent hunting of the comparator when the sensed temperature hovers around a predetermined temperature level. A digital logic network controls visual or sound indicators thereof.
U.S. Pat. No. 3,700,914 of George John Granieri et al discloses a control apparatus for air conditioning systems having a time delay circuit associated with a pressure switch connected in the refrigerant circuit so as to prevent operation of the compressor unless the pressure in the supply line reaches a preselected pressure within a predetermined time interval.
U.S. Pat. No. 3,702,064 of Henry J. Ciolli shows an air conditioning pump shutoff when the level of the system coolant falls below a preselected level. The level is sensed by a thermistor which is immersed in the coolant when it is above the preselected level.
U.S. Pat. No. 3,707,851 of Robert B. McAshan, Jr. shows a refrigeration system efficiency control which incorporates means for effecting a calibration change relative to the ambient air temperature. The control monitors different temperature conditions with a single sensor.
A refrigerant compressor motor control is shown in U.S. Pat. No. 3,721,880 of Donald E. Neill having a temperature sensor for sensing the temperature of the discharge gas from the compressor, and a thermostat for sensing room temperature. The shutdown period is correlated with the time required to reach the shutdown condition so as to provide a variable off period.
U.S. Pat. No. 3,742,303 of Ernest C. Dageford shows a compressor protector system monitoring the temperature within the compressor system and disconnecting the motor when the temperature exceeds a preselected value over a preselected period of time. The control automatically starts the compressor if the fault has been so cleared and prevents short-cycling by preventing attempted restart until after a predetermined period of time. The circuit includes a comparator controlling a semiconductor and electronic switch which, in turn, control the operation of the compressor motor.
Ernest C. Dageford in U.S. Pat. No. 3,743,009 shows an air conditioning and heating control system wherein a thermistor is connected to a comparator to provide a temperature sensing function. A control panel is provided having a plurality of output indicators arranged in rows and columns for indicating different malfunctions in the equipment.
Dean K. Norbeck in U.S. Pat. No. 3,744,267 discloses a control circuit generally similar to that of U.S. Pat. No. 3,707,851 discussed above and utilizing a thermistor which, when contacted by the refrigerant, is cooled to increase its impedance and thereby trigger a switch for interrupting the circuit to the compressor motor.
U.S. Pat. No. 3,780,532 of Dean K. Norbeck et al shows a temperature control system utilizing a two-thermistor sensing unit for sensing the temperature and the rate and direction of the change of the temperature of a fluid in the system. The thermistors are connected to a comparator to provide the desired control function.
U.S. Pat. No. 3,803,863 of Thomas C. Jednacz et al discloses a control system for a refrigeration compressor including thermistor means for sensing the inlet temperature and outlet temperature of the evaporator coil.